Postmenopausal Hormones Reduce the Risk of Colorectal Cancer

According to the results of a study published in Cancer Epidemiology, Biomarkers, & Prevention, use of postmenopausal hormones reduces the risk of colorectal cancer.

Postmenopausal hormone therapy with either estrogen alone or estrogen plus progestin effectively manages several common menopausal symptoms. However, large clinical trials conducted as part of the Women’s Health Initiative (WHI) raised concerns about the health risks of these therapies. In 2002, for example, it was reported that combined estrogen plus progestin increases the risk of breast cancer, heart disease, stroke, and blood clots. Women taking estrogen plus progestin had fewer fractures and were less likely to develop colorectal cancer, but these benefits were thought to be outweighed by the risks for most women.

To further explore the effects of postmenopausal hormones on risk of colorectal cancer, researchers evaluated information from more than 56,000 postmenopausal women who participated in the Breast Cancer Detection Demonstration Project follow up study.

  • Women who had ever used unopposed estrogen (estrogen alone, without progestin) were 17% less likely to develop colorectal cancer than women who had never used postmenopausal hormones. The greatest reduction in risk was observed among current users of estrogen and women who had used estrogen for at least ten years.
  • Ever-use of combined estrogen plus progestin was linked with a 22% reduction in risk of colorectal cancer, but this result was not statistically significant, suggesting that it could have occurred by chance alone.
  • Statistically significant reductions in risk of colorectal cancer were observed in some subsets of women who had used combined hormone therapy. Past-users (women who had stopped using hormones at least five years previously) had a 45% reduction in risk of colorectal cancer compared with never-users, and women who used sequential hormone therapy (combined hormone therapy with progestin given for less than 15 days per month) had a 36% reduction in risk.

These results provide additional evidence that postmenopausal hormone use may reduce the risk of colorectal cancer. Because postmenopausal hormones have a wide range of health effects, however, women who are considering using hormones to manage menopausal symptoms are advised to discuss the risks and benefits with their health care provider.

Reference: Johnson JR, Lacey JV, Lazovich D et al. Menopausal hormone therapy and risk of colorectal cancer. Cancer Epidemiology, Biomarkers, & Prevention. 2009;18:196-203.

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